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Electrostatic and gravitational fields of force: WJEC A‑Level Physics questions

Every WJEC A-Level Physics exam question on 4.2 Electrostatic and gravitational fields of force, 2016–2025, with its mark scheme and examiner’s report.

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1,173 questions

  1. Q1(a)

    Summer 2025 · Unit 4

    1 mark4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2025 Unit 4, question 1(a): The vertical forces are balanced. Explain why the tension, T, in each thread is almost exactly equal to the weight of the spheres. [1]

  2. Q1(b)

    Summer 2025 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2025 Unit 4, question 1(b): Each sphere has a mass of 2.7 g. Show that the repulsive force between the two spheres is approximately 2 mN. [3]

  3. Q1(c)

    Summer 2025 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2025 Unit 4, question 1(c): Each sphere carries a charge of 125 nC. Calculate the distance between the centres of the spheres assuming that the spheres behave as point charges. [3]

  4. Q1(d)(i)

    Summer 2025 · Unit 4

    2 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2025 Unit 4, question 1(d)(i): Define electric potential. [2]

  5. Q1(d)(ii)

    Summer 2025 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2025 Unit 4, question 1(d)(ii): Calculate the electric potential at a point which is 7.0 cm from the centre of one sphere and 18.0 cm from the centre of the other sphere. Assume that both sphe

  6. Q2(a)

    Summer 2025 · Unit 4

    2 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2025 Unit 4, question 2(a): of this statement. [2]

  7. Q2(b)

    Summer 2025 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2025 Unit 4, question 2(b): Draw 4 gravitational field lines and 2 equipotentials for the star. [3]

  8. Q2(c)

    Summer 2025 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2025 Unit 4, question 2(c): Show that the mass of the star is approximately 5 × 1030 kg. [3]

  9. Q4(a)(i)

    Summer 2024 · Unit 4

    1 mark4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2024 Unit 4, question 4(a)(i): Define electric field strength. [1]

  10. Q4(a)(ii)

    Summer 2024 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2024 Unit 4, question 4(a)(ii): Show that the magnitude of the electric field strength at P due to any one of the four charges is approximately 520 kN C−1. [3]

  11. Q4(a)(iii)

    Summer 2024 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2024 Unit 4, question 4(a)(iii): Hence, calculate the resultant electric field strength at P and give its direction. [3]

  12. Q4(b)(i)

    Summer 2024 · Unit 4

    1 mark4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2024 Unit 4, question 4(b)(i): Define electric potential. [1]

  13. Q4(b)(ii)

    Summer 2024 · Unit 4

    2 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2024 Unit 4, question 4(b)(ii): Explain briefly why the potential energy of the negative charge is zero at P. [2]

  14. Q4(b)(iii)

    Summer 2024 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2024 Unit 4, question 4(b)(iii): Aled states “The negative charge initially accelerates to the right, then slows down but will just about reach infinity if no resistive forces act.” Discuss to

  15. Q4(b)(iv)

    Summer 2024 · Unit 4

    5 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2024 Unit 4, question 4(b)(iv): Calculate the speed of the −38 nC charge when it reaches point X shown below. [5] _ 42 μC + 42 μC 1.34 m 0.60 m P X _ 42 μC + 42 μC

  16. Q3(c)(i)

    Summer 2023 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2023 Unit 4, question 3(c)(i): Show that the gravitational potential at the position of a planet due to the star and the other two planets is approximately –1 × 1010 J kg–1. [3]

  17. Q3(c)(ii)

    Summer 2023 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2023 Unit 4, question 3(c)(ii): planets, the planet would gain enough energy to escape the gravitational pull of the star. Discuss to what extent Rhodri’s statement might be correct. [3]

  18. Q6(a)(i)

    Summer 2023 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2023 Unit 4, question 6(a)(i): Show that the potential at the surface of the negative sphere is approximately –7500 V. [3]

  19. Q6(a)(ii)

    Summer 2023 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2023 Unit 4, question 6(a)(ii): Sketch the graph for the electric potential between the two charges (the potential has been plotted for the surface of the negative charge). [3] Potential / kV

  20. Q6(b)

    Summer 2023 · Unit 4

    3 marks4.2 Electrostatic and gravitational fields of force
    The whole paper ↗
    Summer 2023 Unit 4, question 6(b): Explain why the electric field on the right-hand surface of the negative sphere is approximately 810 000 N C–1 and directed towards the left. [3]
All 41 questions on Electrostatic and gravitational fields of force, as a list
  1. Summer 2025, Unit 4, Q1(a) (1 mark): The vertical forces are balanced. Explain why the tension, T, in each thread is almost exactly equal to the weight of the spheres. [1]
  2. Summer 2025, Unit 4, Q1(b) (3 marks): Each sphere has a mass of 2.7 g. Show that the repulsive force between the two spheres is approximately 2 mN. [3]
  3. Summer 2025, Unit 4, Q1(c) (3 marks): Each sphere carries a charge of 125 nC. Calculate the distance between the centres of the spheres assuming that the spheres behave as point charges. [3]
  4. Summer 2025, Unit 4, Q1(d)(i) (2 marks): Define electric potential. [2]
  5. Summer 2025, Unit 4, Q1(d)(ii) (3 marks): Calculate the electric potential at a point which is 7.0 cm from the centre of one sphere and 18.0 cm from the centre of the other sphere. Assume that both sphe
  6. Summer 2025, Unit 4, Q2(a) (2 marks): of this statement. [2]
  7. Summer 2025, Unit 4, Q2(b) (3 marks): Draw 4 gravitational field lines and 2 equipotentials for the star. [3]
  8. Summer 2025, Unit 4, Q2(c) (3 marks): Show that the mass of the star is approximately 5 × 1030 kg. [3]
  9. Summer 2024, Unit 4, Q4(a)(i) (1 mark): Define electric field strength. [1]
  10. Summer 2024, Unit 4, Q4(a)(ii) (3 marks): Show that the magnitude of the electric field strength at P due to any one of the four charges is approximately 520 kN C−1. [3]
  11. Summer 2024, Unit 4, Q4(a)(iii) (3 marks): Hence, calculate the resultant electric field strength at P and give its direction. [3]
  12. Summer 2024, Unit 4, Q4(b)(i) (1 mark): Define electric potential. [1]
  13. Summer 2024, Unit 4, Q4(b)(ii) (2 marks): Explain briefly why the potential energy of the negative charge is zero at P. [2]
  14. Summer 2024, Unit 4, Q4(b)(iii) (3 marks): Aled states “The negative charge initially accelerates to the right, then slows down but will just about reach infinity if no resistive forces act.” Discuss to
  15. Summer 2024, Unit 4, Q4(b)(iv) (5 marks): Calculate the speed of the −38 nC charge when it reaches point X shown below. [5] _ 42 μC + 42 μC 1.34 m 0.60 m P X _ 42 μC + 42 μC
  16. Summer 2023, Unit 4, Q3(c)(i) (3 marks): Show that the gravitational potential at the position of a planet due to the star and the other two planets is approximately –1 × 1010 J kg–1. [3]
  17. Summer 2023, Unit 4, Q3(c)(ii) (3 marks): planets, the planet would gain enough energy to escape the gravitational pull of the star. Discuss to what extent Rhodri’s statement might be correct. [3]
  18. Summer 2023, Unit 4, Q6(a)(i) (3 marks): Show that the potential at the surface of the negative sphere is approximately –7500 V. [3]
  19. Summer 2023, Unit 4, Q6(a)(ii) (3 marks): Sketch the graph for the electric potential between the two charges (the potential has been plotted for the surface of the negative charge). [3] Potential / kV
  20. Summer 2023, Unit 4, Q6(b) (3 marks): Explain why the electric field on the right-hand surface of the negative sphere is approximately 810 000 N C–1 and directed towards the left. [3]
  21. Summer 2022, Unit 4, Q2(a) (3 marks): Draw 2 equipotentials and 4 field lines for both the electric field of the positron and the gravitational field of the anti-neutron shown. [3] Electric field Gr
  22. Summer 2022, Unit 4, Q2(b) (6 marks): Describe and explain the similarities and differences between electric and gravitational fields. [6 QER]
  23. Summer 2022, Unit 4, Q3(a) (4 marks): Draw arrows to show the 3 electric fields at P due to the 3 charges. Use these to explain why the electron will accelerate in the direction shown. [4]
  24. Summer 2022, Unit 4, Q3(b) (4 marks): Calculate the initial acceleration of the electron. [4]
  25. Summer 2022, Unit 4, Q3(c) (2 marks): Show clearly that the initial potential energy of the electron is approximately –6 × 10–18J. [2]
  26. Summer 2022, Unit 4, Q3(d) (4 marks): Determine whether or not the electron (initially at rest) will reach point R, shown in the diagram below (both positive charges are 0.60 m from R). Explain your
  27. Summer 2022, Unit 4, Q5(c) (2 marks): The centre of mass of this two-star system is also the point where the resultant gravitational field strength is zero. Explain why these points only coincide wh
  28. Summer 2019, Unit 3, Q7(c)(i) (3 marks): Calculate the distance of nearest approach for a 4.7 MeV alpha particle when fired at gold foil (the charge on a gold nucleus is +79e, see paragraph 6). [3]
  29. Summer 2019, Unit 4, Q2(a) (3 marks): Assuming that the Earth is an isolated perfect sphere, draw its gravitational field lines and equipotential surfaces. [3]
  30. Summer 2019, Unit 4, Q2(b)(i) (3 marks): Use the information in the diagram to calculate the gravitational potential at point P. [3] ME = 5.97 × 1024 kg MM = 7.37 × 1022 kg P 342 000 km 38 000 km
  31. Summer 2019, Unit 4, Q2(b)(ii) (2 marks): Use the information in the diagram to show that the resultant gravitational field at point P is very small. [2]
  32. Summer 2018, Unit 4, Q2(a)(i) (3 marks): Explain how this equation is an application of conservation of energy. [3]
  33. Summer 2018, Unit 4, Q2(a)(ii) (3 marks): RSun = 6.96 × 108 m). [3]
  34. Summer 2018, Unit 4, Q2(b)(ii) (2 marks): By considering your answers to (a)(ii) and (b)(i), explain why the Sun has a slight positive charge. [2]
  35. Summer 2018, Unit 4, Q2(b)(iii) (3 marks): A student claims that a positive charge of approximately 0.08 C on the Sun is enough to produce an electrostatic force equal to the gravitational force on an es
  36. Summer 2018, Unit 4, Q2(b)(iv) (3 marks): Estimate the percentage of lost electrons compared with the total number of electrons on the Sun. Assume that the Sun is mainly hydrogen and that it has lost 0.
  37. Summer 2017, Unit 4, Q2(a) (2 marks): Draw two arrows on the diagram to represent the directions of the electric fields at C due to the –21 μC and +28 μC charges. [2]
  38. Summer 2017, Unit 4, Q2(b) (5 marks): Calculate the magnitude and direction of the resultant electric field at C. [5]
  39. Summer 2017, Unit 4, Q2(c) (2 marks): Show that the electrical potential at point C is zero. [2]
  40. Summer 2017, Unit 4, Q2(d) (3 marks): A positron is initially at rest at point C and accelerates rapidly due to the electric field. Calculate the potential at the point where the velocity of the pos
  41. Summer 2017, Unit 4, Q3(c)(i) (2 marks): Calculate the potential energy of the star-planet system (see diagram in part (a)). [2]

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